Creating Own Nameservers

I have purchased two domains for two servers. The domain registrar is GoDaddy. I followed the instructions for creating the nameservers in HowToForge and added ns1, and ns2 to GoDaddy's hosts records, where the IPs were accepted. A who-is identifies the ns1 and ns2 perfectly, but intodns.com says these are "lame duck" nameservers (I think this was the term used?) I'm not sure exactly how to correct this. I am not sure if this is an issue that needs to be configured in ISPConfig 3 or it is purely a Linux issue, maybe /etc/hosts ? Any help would be appreciated. I don't mind using GoDaddy's nameservers on my own accounts, but not for other clients or those registered outside of GoDaddy, like Enom, or Network Solutions, etc.

Thanks for the response. What I am trying to achieve is having my own nameservers for a client to use that points to my server. I purchased two domains for this purpose. The nameserver hosts have been created at the domain registrar (GoDaddy), and added to the DNS records in ISPConfig. Still no go. Doing a who-is shows ns1.example.com with the correct IP and likewise for ns2, but they won't resolve the domain that is using them as nameservers. Hopefully this clarifies some?